The present invention concerns a pressure sensor including a body that has a chamber for receiving a pressurized fluid and a support element around said chamber, a cover secured to the body with a stop strip that has a closed contour in correspondence with the support element for the body, a diaphragm, which is arranged between the body and the cover to seal off the pressure chamber and which can bend under the effect of a difference in pressure between the two sides thereof, with a peripheral region of the diaphragm arranged between said support element and said stop strip, and transmission means, connected to a central region of the diaphragm for transmitting diaphragm deflection data to measuring or indicating means. The invention also concerns a depth gauge containing a pressure sensor of this type.
In pressure sensors used, in particular, in manometers or depth gauges, the diaphragm (also called a “membrane”) usually takes the form of a metal disc with concentric corrugations for altering the elastic deflection amplitude. This type of diaphragm can be fixed in the sensor by welding (see for example DE Patent Application No 10147124), but also without welds, for example by clamping, as seen in WO Patent Application No. 01/01098. However, precise manufacture of such diaphragms is quite complicated and the level of reproducibility is not high. Moreover, it is not easy to prevent the diaphragm from undergoing plastic deformation if the sensor is subjected to pressure that exceeds the operating pressure.
It has thus been sought to use flat diaphragms, but the method of securing the diaphragm continues to cause quite significant drawbacks. If the peripheral region of the diaphragm is welded to the sensor structure, this decreases the elastic deformation that the diaphragm can undergo before being plastically deformed; therefore the sensitivity of the sensor is reduced. Moreover, welding introduces different stiffness characteristics for each weld. The resulting diaphragm deflection imprecision evidently reduces the precision of the sensor and, further, makes it difficult to use stop members to prevent plastic deformation of the diaphragm. Securing the diaphragm by insetting it into the sensor structure also leads to some of the aforementioned drawbacks.
We will also mention the possibility of giving a non-welded diaphragm a broad U-shaped profile, with a flat shape surrounded by a vertical edge that cooperates with a sealing gasket. In this case, the diaphragm is quite voluminous, the raised edge is only used for sealing, and, above all, the bends in the U are areas where stresses due to fluid pressure are concentrated, thus limiting the elastic deformation that the diaphragm can undergo prior to entering the plastic domain.